One of the tools that was used to track down the suspect is what's sometimes called an electronic wanted poster. It's believed to be the first time authorities have used the so-called wireless emergency alert system to help track down a suspected terrorist. That system is best known for Amber Alerts and weather emergencies.

A message was blasted to millions of New Yorkers' cell phones describing the man they were looking for. NPR's Tovia Smith reports the tactic is also raising concerns of racial profiling.

TOVIA SMITH, BYLINE: It's hard to overstate its power. In an instant, as New York Police Commissioner James O'Neill told CBS News today, authorities enlisted millions of extra eyeballs to their manhunt.

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COMMISSIONER JAMES O'NEILL: I was truly helpful. We try to think all of us working together, not just law enforcement. I think that's the way we're going to keep the city safe.

KABIR DAYA: I got one, and it was, like - oh, what's this?

SMITH: Kabir Daya says when he got the alert on his cell phone yesterday, he not only wondered where the suspect might be lurking but also whether he himself might be mistaken for the guy.

DAYA: I will be honest. That was a little bit in the back of my head as well. I mean there's always a little tinge of anxiety about that kind of stuff, you know, me looking the way I am. And I have a beard and, you know, a darker complexion. And I clearly look like I wasn't necessarily born here.

SMITH: To some, it's especially concerning now amid a series of incidents in New York targeting Muslims and what some Muslim civil rights advocates call a mainstreaming of Islamophobia. Ibrahim Hooper with the Council on American-Islamic Relations says he's troubled that authorities put out the suspect's name that's obviously Muslim but no description or picture.

SMITH: If you're riding on a train with somebody and you see somebody wearing a headscarf or with a beard or with a darker complexion or somebody you perceive to be Muslim, that could lead to suspicion of that person and some kind of action targeting that person.

SMITH: The message did tell people to see media for pic, hoping they'd go online to get one. But University of Southern Mississippi professor Bandana Kar, who's been studying the alert system for the Department of Homeland Security, says that's like putting up a wanted poster with no picture and could hurt more than it helps.

BANDANA KAR: The open-ended nature of that alert, being very vague, end up generating a lot of false information. Then it confuses the entire system.

SMITH: DHS officials say they will soon make changes that'll allow for longer messages and better descriptions, but attaching images or a link to one, they say, requires further study. Julius Genachowski was chair of the FCC when the system was first launched on the tenth anniversary of 9/11. He says it's an essential tool designed precisely for cases like this.

JULIUS GENACHOWSKI: Yeah, this is too powerful to be put on a shelf. I'd expect and encourage law enforcement authorities to be thoughtful but to find the best way to use them to maximize the benefits and minimize the risks.

SMITH: One other suggestion - after a frightening alert about a suspect on the loose, residents might also appreciate getting an all-clear when the scare is over. Tovia Smith, NPR News, New York. Transcript provided by NPR, Copyright NPR.